‘Seasoning’ of latent damage trails in lunar samples

Abstract

CHARGED particle track analysis has been used extensively in the study of both terrestrial and lunar samples^1–5. In the latter, the tracks are produced by both internal and external sources. A careful analysis of etched track parameters not only helps in identifying various track-producing sources but also yields useful information about their charge and energy spectra. Most of the lunar samples analysed⁶ show that the track parameters of iron group nuclei from solar and galactic sources are very different from and more stable than those produced by (for example) 9.6 MeV per nucleon ⁵⁶Fe ions in simulation experiments in the laboratory. Similar effects are expected for other charged particle tracks. It seems as though the latent damage trails in lunar samples have been ‘seasoned’ or their structures have been so modified by lunar conditions (particularly, lunar temperature and high doses of light charged particles) that significant changes are brought about in their properties.